How They Work

• This class of drugs slows down nerve impulses to the heart by blocking the effect of the hormone epinephrine, also known as adrenaline, on the body's beta receptors. This results in a slower and less forceful heart beat and a reduction in blood pressure. According to the Cedars-Sinai Heart Institute, beta blockers also reduce the nerve impulses that can cause the potentially deadly heart rhythm abnormalities known as arrhythmias.
  
  

Types of Beta Blockers

• Not all beta blockers are created equal, according to eMedTV. Those described as cardioselective focus primarily on the heart and blood vessels and include such drugs as acebutolol, atenolol, betaxolol, bisoprolol, esmolol, metoprolol and nebivolol. Beta blockers with intrinsic sympathomimetic activity (ISA) not only block beta receptors but also provide them with subtle stimulation; these drugs include carteolol, penbutolol and pindolol. Beta blockers that also block alpha receptors include carvedilol and labetalol.
  
  

Less Oxygen Circulating

• In slowing the heart rate to ease the workload the heart must carry, beta blockers also reduce the flow of oxygen to various parts of the body. This often results in a lack of endurance and feelings of weakness when performing strenuous tasks, according to the American Heart Association. Another common side effect that can be traced to reduced oxygen circulation is nausea that follows any physical exertion. The AHA suggests that patients taking beta blockers "should avoid activities that normally made their hearts beat faster in the past, such as heavy cleaning, grass cutting or lifting. Otherwise, they can feel quite ill for more than a day after performing such activities."
  
  

Other Side Effects

• Other common side effects, according to the Texas Heart Institute, include cold hands and feet; dizziness; and dry mouth, eyes and skin. Less common side effects include shortness of breath; sleeping difficulties; vivid dreams, including nightmares; abnormally low blood pressure; and swelling of the feet and hands. Rare side effects include abdominal cramps, constipation, diarrhea, depression, vomiting, joint pain, sore throat, mental confusion, memory loss and sexual dysfunction.
  
  

Drug Interactions

• Beta blockers may have unwelcome interactions with drugs that are being taken for the treatment of asthma, chronic bronchitis and emphysema; certain antidepressants; drugs that include antihistamines; insulin in both injectable and oral form; and other medications to treat hypertension.